The majority of substantive health monitoring features require FDA approval. The Apple Watch has Class II medical device certification but only for ECG and Afib monitoring but the device could still incorporate additional health functions that do not require FDA approval.
Features such as blood oxygen level monitoring via the SpO2 sensor on Apple Series 6 have not been put through the rigors of FDA certification. Instead, an appropriate disclaimer “not a medical device”, is used on the product description page.
The same is true for other wearable manufacturers such as Fitbit or Samsung that have the ECG functions today.
A newly published Apple Watch continuation patent caught our attention. The Patent was filed on March 1, 2021, and was published today (June 17th,2021).
The detailed section of this patent incorporates a section where the investors describe incremental functions using the electrodes on the back of the watch.
“The device may also include at least one pair of electrodes disposed on an exterior surface of the wearable electronic device. The electrodes may be configured to produce a second sensor signal when the electrodes are in contact with a respective portion of the body.”
Although the electrodes present currently on the Apple Watch help with heart rate monitoring, here is the section that describes additional features such as estimating body fat percentage.
How can Smartwatch electrode sensors help with body fat estimation?
Is it possible for smartwatches to use built-in miniature electrodes to estimate body fat percentage? Can this be used for meaningful obesity management?
Existing research shows that it is possible for a wrist-based bioelectrical impedance analyzer with miniature electrodes to compute body fat estimates.
Bioimpedance analysis is a non-invasive, low cost and commonly used approach for body composition measurements and assessment of clinical conditions.
The premise of bioimpedance-based BMI(body mass index) estimation is that fat conducts electricity at a different rate than the rest of your body (water, muscle, bone). Most digital body scales out there today use bioimpedance to estimate body fat percentage.
Studies around bioimpedance are not new. While some of these studies focussed on estimating body hydration, Nyboer’s study on Electrical impedance Plethysmography was one of the first ones that focussed on estimating fat free mass using quad surface electrode readings for bioimpedance measurements.
Samsung Electronics Research Study results, Jan 2021
More recently, a new study published in the Nature journal shows that it is very much possible to estimate body fat percentage using miniature electrodes and bioimpedance analysis.
Samsung Electronics researchers used miniature electrodes (196 mm2). The total area of finger electrodes (a pair of one current electrode and one voltage electrode on the top side of the device) was 68 mm2 and that of wrist electrodes (another pair of one current electrode and one voltage electrode on the bottom side of the device) was 128 mm2.
The internal microcontroller unit of BioProcessor2 calculated body fat, lean body mass, and body water volume using impedance data and user profile information such as height, age, weight, and gender.
It is very likely we could see some of these new features in the upcoming Galaxy Watch 4 soon to be unveiled. Samsung had also filed a patent way back in 2019 regarding the functionality of estimating body fat percentage using the watch.
The researchers on this paper were all employees of Samsung Electronics Healthcare Research Lab and used the AFE (S3FBP5A, BioProcessor2, Samsung Electronics) to deliver 30 μA sinusoidal alternating current with 50 kHz frequency to the two current electrodes and measure the voltage drop between the two voltage electrodes.
To evaluate the accuracy of the wrist-based bioelectrical impedance analyzer, a clinical test was conducted on 203 volunteers who were recruited at Seoul St. Mary’s Hospital. The study population consisted of 18‒68-year-old healthy male (n = 101) and female (n = 102) volunteers.
The wrist-wearable device used by the researchers (R = 0.899, SEE = 3.8%BF) produced more accurate results than a commercial upper-body portable body fat analyzer (R = 0.893, SEE = 4.7%BF), more so with quite a smaller size of electrodes. The commercial body fat analyzer used for comparison purposes was the OMRON HBF-306.
So, this study shows that technically it is very much possible to leverage the microelectrodes embedded on the smartwatch to calculate body fat percentage, lean body mass, and body water volume quite accurately using bio-impedance.
In the case of the Apple Watch, the crystal electrodes on the back of the watch combined with the digital crown electrode could potentially help with bioimpedance analysis thereby helping with developing body fat estimates, lean mass estimates, and more.
Fitness bands in the past such as TomTom’s Touch Cardio band, released in 2017 and ALFAWISE T9, released sometime in 2019 had body fat estimation features, so this won’t be a feature that is dramatically new or has not been tested before.
As with any patent, it is hard to say if they will ever make it to the actual product. Given that this feature will not require any regulatory approvals, it is possible that the upcoming smartwatches from Apple, Samsung, or Fitbit could soon house this feature that will help people in their fight against obesity.
Although the idea was spotted on an Apple Wearable device patent, we believe that Samsung Galaxy watches could be the first ones to come out with the body fat estimation feature, given that the research and study results were published based on Samsung Biosensor hardware earlier this year.
